Best plywood

I am thinking about about building a Weekender or a Long Weekender and I want to Know What plywood is best?
I was probably going to Use Marine Fir at least for the bottom and exterior. I was just going to seal it with marine epoxy and boat paint or one of the other sealers.
Is osb good to use? It is used in the weekender build photos. It looks heavy.
Also what about the new green plywood?
Also How should I seal the interior to stop formaldehyde vapors? I saw about Katrina trailers having vapor issues on the news.
I also thought I might buy a used boat trailer on ebay or craigs list to start the trailer on. Any thoughts.
thanks Sean from Texas
I was probably going to Use Marine Fir at least for the bottom and exterior. I was just going to seal it with marine epoxy and boat paint or one of the other sealers.
Is osb good to use? It is used in the weekender build photos. It looks heavy.
Also what about the new green plywood?
Also How should I seal the interior to stop formaldehyde vapors? I saw about Katrina trailers having vapor issues on the news.
I also thought I might buy a used boat trailer on ebay or craigs list to start the trailer on. Any thoughts.

thanks Sean from Texas